The present invention relates to very fine denier polyester yarn made from poly(trimethylene terephthalate) fibers.
Polyester yarns having very fine denier are highly desirable for manufacturing fabrics used in the garment industry. Such yarns are desirable because they yield a light-weight material having excellent properties such as softness. The softness of a yarn and fabric is a measure of how soft a material feels to the touch. A yarn and fabric used for many clothing apparel items require a high degree of softness.
Very fine denier polyester fibers currently known in the art are made using polyethylene terephthalate. Such yarns provide softness suitable for many garments such as, e.g., dresses, jackets and other ladies"" apparel. However, because polyethylene terephthalate has a high Young""s modulus, the maximum softness achieved is not suitable for garments requiring ultra-soft touch.
There is therefore a need in the art for very fine denier polyester yarns having superior softness quality. Theoretically, polyester yarns made from a polymer having a low Young""s modulus should yield the desirable properties. However, attempts to commercially manufacture such a fine denier polyester yarn from poly(trimethylene terephthalate) have not been successful due to various manufacturing problems. For example, when attempting to make very fine denier yarns from poly(trimethylene terephthalate), excessive breaks in the fibers have been experienced. Further, it was thought in the prior art that the tenacity of poly(trimethylene terephthalate) was too low to successfully make a very fine denier yarn.
The invention is directed to a process for making a drawn yarn from a partially oriented feed yarn, comprising the steps of:
(1) providing a polyester polymer having an intrinsic viscosity of at least 0.80 dl/g comprising at least 85 mole % poly(trimethylene terephthalate) wherein at least 85 mole % of repeating units consist of trimethylene units;
(2) spinning the polyester polymer by melt-extruding the polyester polymer at a temperature between about 255xc2x0 C. and 275xc2x0 C. to form a partially oriented feed yarn;
(3) preparing a drawn yarn from the partially oriented feed yarn, wherein said drawn yarn has the following characteristics:
(a) a denier per filament less than about 1.0; and
(b) an actual draw ratio within 10 percent of a predicted draw ratio, wherein the predicted draw ratio is determined according to: [(elongation to break of the feed yarn)+115]/[(elongation to break of the drawn yarn)+115)].
Preferably the actual draw ratio is within 5 percent of the predicted draw ratio. More preferably the actual draw ratio is within 3 percent of the predicted draw ratio.
Preferably step (a) comprises extruding the molten polymer at a temperature between 260xc2x0 C. and 270xc2x0 C. More preferably step (a) comprises extruding the molten polymer at a temperature of at least 265xc2x0 C.
Preferably the spinneret has orifices between about 0.12 to 0.38 mm in diameter.
Preferably the denier per filament of the drawn yarn is less than about 1.0.
The invention is also directed to a process for making a drawn yarn comprising:
(a) providing partially oriented feed yarn filaments prepared from a polyester polymer having an intrinsic viscosity of at least 0.80 dl/g comprising at least 85 mole % poly(trimethylene terephthalate) wherein at least 85 mole % of repeating units consist of trimethylene units; and
(b) drawing the filaments between a set of feed rolls to produce a denier per filament less than about 1.5 and an actual draw ratio within 10 percent of a predicted draw ratio, wherein the predicted draw ratio is determined according to: [(elongation to break of the feed yarn)+115]/[(elongation to break of the drawn yarn)+115)]. Preferably, this process further comprises heating the filaments to a temperature greater than the glass transition temperature of the filaments, but less than 200xc2x0 C., prior to drawing the filaments. Preferably this process further comprises preparing the partially oriented feed yarn filaments by extruding the polyester in a molten state a temperature between about 255xc2x0 C. and 275xc2x0 C. through a spinneret to form filaments.
Preferably the process comprises interlacing the filaments prior to drawing them.
The actual draw ratio is preferably within 5 percent of the predicted draw ratio, more preferably within 3 percent of the predicted draw ratio.
Preferably the denier per filament of the drawn yarn is less than 1.0.
Preferably the provided partially oriented feed yarn filaments have a denier per filament less than about 2.
Preferably the polyester is melt-extruded on a spinneret having orifices between about 0.12 to 0.38 mm in diameter.
The invention is also directed to the process wherein the drawing comprises warp drawing or single end drawing and further comprising air jet texturing or false-twisting.
The invention is further directed to a process of preparing a fine denier partially oriented undrawn feed yarn made from a polyester polymer melt-extruded at a spinning temperature between about 255xc2x0 C. and about 275xc2x0 C., wherein said polymer comprises at least 85 mole % poly(trimethylene terephthalate) wherein at least 85 mole % of repeating units consist of trimethylene units, and wherein said polymer has an intrinsic viscosity of at least 0.80 dl/g, and wherein said partially oriented undrawn fine denier feed yarn has a denier per filament less than about 2. Preferably the undrawn filaments have a denier per filament less than about 1.5, more preferably less than about 1.0.
The present invention also comprises a drawn yarn made from a partially oriented feed yarn, said feed yarn made from a polyester polymer melt-extruded at a spinning temperature between about 255xc2x0 C. and 275xc2x0 C., wherein said polymer comprises at least 85 mole % poly(trimethylene terephthalate) wherein at least 85 mole % of repeating units consist of trimethylene units, and wherein said polymer has an intrinsic viscosity of at least 0.80 dl/g, and wherein said drawn yarn has the following characteristics:
(a) a denier per filament less than about 1.5; and
(b) an actual draw ratio within 10 percent of a predicted draw ratio, wherein the predicted draw ratio is determined according to: [(elongation to break of the feed yarn)+115]/[(elongation to break of the drawn yarn)+115)].
The present invention further comprises a process for making a drawn yarn from a partially oriented feed yarn, comprising the steps:
(a) extruding a molten polyester polymer at a temperature between about 255xc2x0 C. and about 275xc2x0 C. through a spinneret to form filaments, wherein said polymer comprises at least 85 mole % poly(trimethylene terephthalate) wherein at least 85 mole % of repeating units consist of trimethylene units, and wherein said polymer has an intrinsic viscosity of at least 0.80 dl/g;
(b) cooling the filaments by exposing them to a flow of quench air;
(c) coating the filaments with a spin finish;
(d) heating the filaments to a temperature greater than the glass transition temperature of the filaments, but less than 200xc2x0 C., prior to drawing the filaments; and
(e) drawing the filaments between a set of feed rolls to produce a denier per filament less than about 1.5 and an actual draw ratio within 10 percent of a predicted draw ratio, wherein the predicted draw ratio is determined according to: [(elongation to break of the feed yarn)+115]/[(elongation to break of the drawn yarn)+115)].
The present inventions also comprises a fine denier feed yarn made from a polyester polymer melt-extruded at a spinning temperature between about 255xc2x0 C. and about 275xc2x0 C., wherein said polymer comprises at least 85 mole % poly(trimethylene terephthalate) wherein at least 85 mole % of repeating units consist of trimethylene units, and wherein said polymer has an intrinsic viscosity of at least 0.80 dl/g, and wherein said fine denier feed yarn has a denier per filament less than about 2.